I prefer PS3 since it is in fact the cheapest(and most future proof) Blu-Ray player along with being a video game console.

That said 360 currently has better games with titles like Gears of War,Bioshock, and Mass Effect being exclusive. If you are into shooters than 360 is clearly the choice for you. Down the line PS3 will get Metal Gear Solid 4, Final Fantasy XIII, and Final Fantasy Versus 13 as exclusives though.